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• Using TPL and PLINQ to raise performance of feed aggregator

  - by DigiMortal

  In this posting I will show you how to use Task Parallel Library (TPL) and PLINQ features to boost performance of simple RSS-feed aggregator. I will use here only very basic .NET classes that almost every developer starts from when learning parallel programming. Of course, we will also measure how every optimization affects performance of feed aggregator. Feed aggregator Our feed aggregator works as follows: Load list of blogs Download RSS-feed Parse feed XML Add new posts to database Our feed aggregator is run by task scheduler after every 15 minutes by example. We will start our journey with serial implementation of feed aggregator. Second step is to use task parallelism and parallelize feeds downloading and parsing. And our last step is to use data parallelism to parallelize database operations. We will use Stopwatch class to measure how much time it takes for aggregator to download and insert all posts from all registered blogs. After every run we empty posts table in database. Serial aggregation Before doing parallel stuff let’s take a look at serial implementation of feed aggregator. All tasks happen one after other. internal class FeedClient {     private readonly INewsService _newsService;     private const int FeedItemContentMaxLength = 255;       public FeedClient()     {          ObjectFactory.Initialize(container =>          {              container.PullConfigurationFromAppConfig = true;          });           _newsService = ObjectFactory.GetInstance<INewsService>();     }       public void Execute()     {         var blogs = _newsService.ListPublishedBlogs();           for (var index = 0; index <blogs.Count; index++)         {              ImportFeed(blogs[index]);         }     }       private void ImportFeed(BlogDto blog)     {         if(blog == null)             return;         if (string.IsNullOrEmpty(blog.RssUrl))             return;           var uri = new Uri(blog.RssUrl);         SyndicationContentFormat feedFormat;           feedFormat = SyndicationDiscoveryUtility.SyndicationContentFormatGet(uri);           if (feedFormat == SyndicationContentFormat.Rss)             ImportRssFeed(blog);         if (feedFormat == SyndicationContentFormat.Atom)             ImportAtomFeed(blog);                 }       private void ImportRssFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = RssFeed.Create(uri);           foreach (var item in feed.Channel.Items)         {             SaveRssFeedItem(item, blog.Id, blog.CreatedById);         }     }       private void ImportAtomFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = AtomFeed.Create(uri);           foreach (var item in feed.Entries)         {             SaveAtomFeedEntry(item, blog.Id, blog.CreatedById);         }     } } Serial implementation of feed aggregator downloads and inserts all posts with 25.46 seconds. Task parallelism Task parallelism means that separate tasks are run in parallel. You can find out more about task parallelism from MSDN page Task Parallelism (Task Parallel Library) and Wikipedia page Task parallelism. Although finding parts of code that can run safely in parallel without synchronization issues is not easy task we are lucky this time. Feeds import and parsing is perfect candidate for parallel tasks. We can safely parallelize feeds import because importing tasks doesn’t share any resources and therefore they don’t also need any synchronization. After getting the list of blogs we iterate through the collection and start new TPL task for each blog feed aggregation. internal class FeedClient {     private readonly INewsService _newsService;     private const int FeedItemContentMaxLength = 255;       public FeedClient()     {          ObjectFactory.Initialize(container =>          {              container.PullConfigurationFromAppConfig = true;          });           _newsService = ObjectFactory.GetInstance<INewsService>();     }       public void Execute()     {         var blogs = _newsService.ListPublishedBlogs();                var tasks = new Task[blogs.Count];           for (var index = 0; index <blogs.Count; index++)         {             tasks[index] = new Task(ImportFeed, blogs[index]);             tasks[index].Start();         }           Task.WaitAll(tasks);     }       private void ImportFeed(object blogObject)     {         if(blogObject == null)             return;         var blog = (BlogDto)blogObject;         if (string.IsNullOrEmpty(blog.RssUrl))             return;           var uri = new Uri(blog.RssUrl);         SyndicationContentFormat feedFormat;           feedFormat = SyndicationDiscoveryUtility.SyndicationContentFormatGet(uri);           if (feedFormat == SyndicationContentFormat.Rss)             ImportRssFeed(blog);         if (feedFormat == SyndicationContentFormat.Atom)             ImportAtomFeed(blog);                }       private void ImportRssFeed(BlogDto blog)     {          var uri = new Uri(blog.RssUrl);          var feed = RssFeed.Create(uri);           foreach (var item in feed.Channel.Items)          {              SaveRssFeedItem(item, blog.Id, blog.CreatedById);          }     }     private void ImportAtomFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = AtomFeed.Create(uri);           foreach (var item in feed.Entries)         {             SaveAtomFeedEntry(item, blog.Id, blog.CreatedById);         }     } } You should notice first signs of the power of TPL. We made only minor changes to our code to parallelize blog feeds aggregating. On my machine this modification gives some performance boost – time is now 17.57 seconds. Data parallelism There is one more way how to parallelize activities. Previous section introduced task or operation based parallelism, this section introduces data based parallelism. By MSDN page Data Parallelism (Task Parallel Library) data parallelism refers to scenario in which the same operation is performed concurrently on elements in a source collection or array. In our code we have independent collections we can process in parallel – imported feed entries. As checking for feed entry existence and inserting it if it is missing from database doesn’t affect other entries the imported feed entries collection is ideal candidate for parallelization. internal class FeedClient {     private readonly INewsService _newsService;     private const int FeedItemContentMaxLength = 255;       public FeedClient()     {          ObjectFactory.Initialize(container =>          {              container.PullConfigurationFromAppConfig = true;          });           _newsService = ObjectFactory.GetInstance<INewsService>();     }       public void Execute()     {         var blogs = _newsService.ListPublishedBlogs();                var tasks = new Task[blogs.Count];           for (var index = 0; index <blogs.Count; index++)         {             tasks[index] = new Task(ImportFeed, blogs[index]);             tasks[index].Start();         }           Task.WaitAll(tasks);     }       private void ImportFeed(object blogObject)     {         if(blogObject == null)             return;         var blog = (BlogDto)blogObject;         if (string.IsNullOrEmpty(blog.RssUrl))             return;           var uri = new Uri(blog.RssUrl);         SyndicationContentFormat feedFormat;           feedFormat = SyndicationDiscoveryUtility.SyndicationContentFormatGet(uri);           if (feedFormat == SyndicationContentFormat.Rss)             ImportRssFeed(blog);         if (feedFormat == SyndicationContentFormat.Atom)             ImportAtomFeed(blog);                }       private void ImportRssFeed(BlogDto blog)     {         var uri = new Uri(blog.RssUrl);         var feed = RssFeed.Create(uri);           feed.Channel.Items.AsParallel().ForAll(a =>         {             SaveRssFeedItem(a, blog.Id, blog.CreatedById);         });      }        private void ImportAtomFeed(BlogDto blog)      {         var uri = new Uri(blog.RssUrl);         var feed = AtomFeed.Create(uri);           feed.Entries.AsParallel().ForAll(a =>         {              SaveAtomFeedEntry(a, blog.Id, blog.CreatedById);         });      } } We did small change again and as the result we parallelized checking and saving of feed items. This change was data centric as we applied same operation to all elements in collection. On my machine I got better performance again. Time is now 11.22 seconds. Results Let’s visualize our measurement results (numbers are given in seconds). As we can see then with task parallelism feed aggregation takes about 25% less time than in original case. When adding data parallelism to task parallelism our aggregation takes about 2.3 times less time than in original case. More about TPL and PLINQ Adding parallelism to your application can be very challenging task. You have to carefully find out parts of your code where you can safely go to parallel processing and even then you have to measure the effects of parallel processing to find out if parallel code performs better. If you are not careful then troubles you will face later are worse than ones you have seen before (imagine error that occurs by average only once per 10000 code runs). Parallel programming is something that is hard to ignore. Effective programs are able to use multiple cores of processors. Using TPL you can also set degree of parallelism so your application doesn’t use all computing cores and leaves one or more of them free for host system and other processes. And there are many more things in TPL that make it easier for you to start and go on with parallel programming. In next major version all .NET languages will have built-in support for parallel programming. There will be also new language constructs that support parallel programming. Currently you can download Visual Studio Async to get some idea about what is coming. Conclusion Parallel programming is very challenging but good tools offered by Visual Studio and .NET Framework make it way easier for us. In this posting we started with feed aggregator that imports feed items on serial mode. With two steps we parallelized feed importing and entries inserting gaining 2.3 times raise in performance. Although this number is specific to my test environment it shows clearly that parallel programming may raise the performance of your application significantly.

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• Entity Framework Code First: Get Entities From Local Cache or the Database

  - by Ricardo Peres

  Entity Framework Code First makes it very easy to access local (first level) cache: you just access the DbSet<T>.Local property. This way, no query is sent to the database, only performed in already loaded entities. If you want to first search local cache, then the database, if no entries are found, you can use this extension method: 1: public static class DbContextExtensions 2: { 3: public static IQueryable<T> LocalOrDatabase<T>(this DbContext context, Expression<Func<T, Boolean>> expression) where T : class 4: { 5: IEnumerable<T> localResults = context.Set<T>().Local.Where(expression.Compile()); 6:  7: if (localResults.Any() == true) 8: { 9: return (localResults.AsQueryable()); 10: } 11:  12: IQueryable<T> databaseResults = context.Set<T>().Where(expression); 13:  14: return (databaseResults); 15: } 16: }

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• Google Webmaster Tools reports fake 404 errors

  - by Edgar Quintero

  I have a website where Google Webmaster Tools reports 15,000 links as 404 errors. However, all links return a 200 when I visit them. The problem is, that eventhough I can visit these pages and return a 200, all those 15,000 pages won't index in Google. They aren't appearing in search results. These are constant errors Google Webmaster Tools keeps reporting and I'm not sure what the problem is. We've thought of a DNS issue, but it shouldn't be a DNS issue, because if it were, no page would be indexed (I have 10,000 perfectly indexed). Regarding URL parameters, my pages do not share a similarity in URL parameters that can make it obvious to me what could be causing the error.

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• Project Euler 9: (Iron)Python

  - by Ben Griswold

  In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 9.  As always, any feedback is welcome. # Euler 9 # http://projecteuler.net/index.php?section=problems&id=9 # A Pythagorean triplet is a set of three natural numbers, # a b c, for which, # a2 + b2 = c2 # For example, 32 + 42 = 9 + 16 = 25 = 52. # There exists exactly one Pythagorean triplet for which # a + b + c = 1000. Find the product abc. import time start = time.time() product = 0 def pythagorean_triplet(): for a in range(1,501): for b in xrange(a+1,501): c = 1000 - a - b if (a*a + b*b == c*c): return a*b*c print pythagorean_triplet() print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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• Making your WCF Web Apis to speak in multiple languages

  - by cibrax

  One of the key aspects of how the web works today is content negotiation. The idea of content negotiation is based on the fact that a single resource can have multiple representations, so user agents (or clients) and servers can work together to chose one of them. The http specification defines several “Accept” headers that a client can use to negotiate content with a server, and among all those, there is one for restricting the set of natural languages that are preferred as a response to a request, “Accept-Language”. For example, a client can specify “es” in this header for specifying that he prefers to receive the content in spanish or “en” in english. However, there are certain scenarios where the “Accept-Language” header is just not enough, and you might want to have a way to pass the “accepted” language as part of the resource url as an extension. For example, http://localhost/ProductCatalog/Products/1.es” returns all the descriptions for the product with id “1” in spanish. This is useful for scenarios in which you want to embed the link somewhere, such a document, an email or a page.  Supporting both scenarios, the header and the url extension, is really simple in the new WCF programming model. You only need to provide a processor implementation for any of them. Let’s say I have a resource implementation as part of a product catalog I want to expose with the WCF web apis. [ServiceContract][Export]public class ProductResource{ IProductRepository repository;  [ImportingConstructor] public ProductResource(IProductRepository repository) { this.repository = repository; }  [WebGet(UriTemplate = "{id}")] public Product Get(string id, HttpResponseMessage response) { var product = repository.GetById(int.Parse(id)); if (product == null) { response.StatusCode = HttpStatusCode.NotFound; response.Content = new StringContent(Messages.OrderNotFound); }  return product; }} The Get method implementation in this resource assumes the desired culture will be attached to the current thread (Thread.CurrentThread.Culture). Another option is to pass the desired culture as an additional argument in the method, so my processor implementation will handle both options. This method is also using an auto-generated class for handling string resources, Messages, which is available in the different cultures that the service implementation supports. For example, Messages.resx contains “OrderNotFound”: “Order Not Found” Messages.es.resx contains “OrderNotFound”: “No se encontro orden” The processor implementation bellow tackles the first scenario, in which the desired language is passed as part of the “Accept-Language” header. public class CultureProcessor : Processor<HttpRequestMessage, CultureInfo>{ string defaultLanguage = null;  public CultureProcessor(string defaultLanguage = "en") { this.defaultLanguage = defaultLanguage; this.InArguments[0].Name = HttpPipelineFormatter.ArgumentHttpRequestMessage; this.OutArguments[0].Name = "culture"; }  public override ProcessorResult<CultureInfo> OnExecute(HttpRequestMessage request) { CultureInfo culture = null; if (request.Headers.AcceptLanguage.Count > 0) { var language = request.Headers.AcceptLanguage.First().Value; culture = new CultureInfo(language); } else { culture = new CultureInfo(defaultLanguage); }  Thread.CurrentThread.CurrentCulture = culture; Messages.Culture = culture;  return new ProcessorResult<CultureInfo> { Output = culture }; }}   As you can see, the processor initializes a new CultureInfo instance with the value provided in the “Accept-Language” header, and set that instance to the current thread and the auto-generated resource class with all the messages. In addition, the CultureInfo instance is returned as an output argument called “culture”, making possible to receive that argument in any method implementation   The following code shows the implementation of the processor for handling languages as url extensions.   public class CultureExtensionProcessor : Processor<HttpRequestMessage, Uri>{ public CultureExtensionProcessor() { this.OutArguments[0].Name = HttpPipelineFormatter.ArgumentUri; }  public override ProcessorResult<Uri> OnExecute(HttpRequestMessage httpRequestMessage) { var requestUri = httpRequestMessage.RequestUri.OriginalString;  var extensionPosition = requestUri.LastIndexOf(".");  if (extensionPosition > -1) { var extension = requestUri.Substring(extensionPosition + 1);  var query = httpRequestMessage.RequestUri.Query;  requestUri = string.Format("{0}?{1}", requestUri.Substring(0, extensionPosition), query); ;  var uri = new Uri(requestUri);  httpRequestMessage.Headers.AcceptLanguage.Clear();  httpRequestMessage.Headers.AcceptLanguage.Add(new StringWithQualityHeaderValue(extension));  var result = new ProcessorResult<Uri>();  result.Output = uri;  return result; }  return new ProcessorResult<Uri>(); }} The last step is to inject both processors as part of the service configuration as it is shown bellow, public void RegisterRequestProcessorsForOperation(HttpOperationDescription operation, IList<Processor> processors, MediaTypeProcessorMode mode){ processors.Insert(0, new CultureExtensionProcessor()); processors.Add(new CultureProcessor());} Once you configured the two processors in the pipeline, your service will start speaking different languages :). Note: Url extensions don’t seem to be working in the current bits when you are using Url extensions in a base address. As far as I could see, ASP.NET intercepts the request first and tries to route the request to a registered ASP.NET Http Handler with that extension. For example, “http://localhost/ProductCatalog/products.es” does not work, but “http://localhost/ProductCatalog/products/1.es” does.

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• Why is a fully transparent pixel still rendered?

  - by Mr Bell

  I am trying to make a pixel shader that achieves an effect similar to this video http://www.youtube.com/watch?v=f1uZvurrhig&feature=related My basic idea is render the scene to a temp render target then Render the previously rendered image with a slight fade on to another temp render target Draw the current scene on top of that Draw the results on to a render target that persists between draws Draw the results on to the screen But I am having problems with the fading portion. If I have my pixel shader return a color with its A component set to 0, shouldn't that basically amount to drawing nothing? (Assuming that sprite batch blend mode is set to AlphaBlend) To test this I have my pixel shader return a transparent red color. Instead of nothing being drawn, it draws a partially transparent red box. I hope that my question makes sense, but if it doesnt please ask me to clarify Here is the drawing code public override void Draw(GameTime gameTime) { GraphicsDevice.SamplerStates[1] = SamplerState.PointWrap; drawImageOnClearedRenderTarget(presentationTarget, tempRenderTarget, fadeEffect); drawImageOnRenderTarget(sceneRenderTarget, tempRenderTarget); drawImageOnClearedRenderTarget(tempRenderTarget, presentationTarget); GraphicsDevice.SetRenderTarget(null); drawImage(backgroundTexture); drawImage(presentationTarget); base.Draw(gameTime); } private void drawImage(Texture2D image, Effect effect = null) { spriteBatch.Begin(0, BlendState.AlphaBlend, SamplerState.PointWrap, null, null, effect); spriteBatch.Draw(image, new Rectangle(0, 0, width, height), Color.White); spriteBatch.End(); } private void drawImageOnRenderTarget(Texture2D image, RenderTarget2D target, Effect effect = null) { GraphicsDevice.SetRenderTarget(target); drawImage(image, effect); } private void drawImageOnClearedRenderTarget(Texture2D image, RenderTarget2D target, Effect effect = null) { GraphicsDevice.SetRenderTarget(target); GraphicsDevice.Clear(Color.Transparent); drawImage(image, effect); } Here is the fade pixel shader sampler TextureSampler : register(s0); float4 PixelShaderFunction(float2 texCoord : TEXCOORD0) : COLOR0 { float4 c = 0; c = tex2D(TextureSampler, texCoord); //c.a = clamp(c.a - 0.05, 0, 1); c.r = 1; c.g = 0; c.b = 0; c.a = 0; return c; } technique Fade { pass Pass1 { PixelShader = compile ps_2_0 PixelShaderFunction(); } }

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• Unable to cast transparent proxy to type &lt;type&gt;

  - by Rick Strahl

  This is not the first time I've run into this wonderful error while creating new AppDomains in .NET and then trying to load types and access them across App Domains. In almost all cases the problem I've run into with this error the problem comes from the two AppDomains involved loading different copies of the same type. Unless the types match exactly and come exactly from the same assembly the typecast will fail. The most common scenario is that the types are loaded from different assemblies - as unlikely as that sounds. An Example of Failure To give some context, I'm working on some old code in Html Help Builder that creates a new AppDomain in order to parse assembly information for documentation purposes. I create a new AppDomain in order to load up an assembly process it and then immediately unload it along with the AppDomain. The AppDomain allows for unloading that otherwise wouldn't be possible as well as isolating my code from the assembly that's being loaded. The process to accomplish this is fairly established and I use it for lots of applications that use add-in like functionality - basically anywhere where code needs to be isolated and have the ability to be unloaded. My pattern for this is: Create a new AppDomain Load a Factory Class into the AppDomain Use the Factory Class to load additional types from the remote domain Here's the relevant code from my TypeParserFactory that creates a domain and then loads a specific type - TypeParser - that is accessed cross-AppDomain in the parent domain:public class TypeParserFactory : System.MarshalByRefObject,IDisposable { …/// <summary> /// TypeParser Factory method that loads the TypeParser /// object into a new AppDomain so it can be unloaded. /// Creates AppDomain and creates type. /// </summary> /// <returns></returns> public TypeParser CreateTypeParser() { if (!CreateAppDomain(null)) return null; /// Create the instance inside of the new AppDomain /// Note: remote domain uses local EXE's AppBasePath!!! TypeParser parser = null; try { Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); } catch (Exception ex) { this.ErrorMessage = ex.GetBaseException().Message; return null; } return parser; } private bool CreateAppDomain(string lcAppDomain) { if (lcAppDomain == null) lcAppDomain = "wwReflection" + Guid.NewGuid().ToString().GetHashCode().ToString("x"); AppDomainSetup setup = new AppDomainSetup(); // *** Point at current directory setup.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory; //setup.PrivateBinPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"); this.LocalAppDomain = AppDomain.CreateDomain(lcAppDomain,null,setup); // Need a custom resolver so we can load assembly from non current path AppDomain.CurrentDomain.AssemblyResolve += new ResolveEventHandler(CurrentDomain_AssemblyResolve); return true; } …} Note that the classes must be either [Serializable] (by value) or inherit from MarshalByRefObject in order to be accessible remotely. Here I need to call methods on the remote object so all classes are MarshalByRefObject. The specific problem code is the loading up a new type which points at an assembly that visible both in the current domain and the remote domain and then instantiates a type from it. This is the code in question:Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; parser = (TypeParser) this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); The last line of code is what blows up with the Unable to cast transparent proxy to type <type> error. Without the cast the code actually returns a TransparentProxy instance, but the cast is what blows up. In other words I AM in fact getting a TypeParser instance back but it can't be cast to the TypeParser type that is loaded in the current AppDomain. Finding the Problem To see what's going on I tried using the .NET 4.0 dynamic type on the result and lo and behold it worked with dynamic - the value returned is actually a TypeParser instance: Assembly assembly = Assembly.GetExecutingAssembly(); string assemblyPath = Assembly.GetExecutingAssembly().Location; object objparser = this.LocalAppDomain.CreateInstanceFrom(assemblyPath, typeof(TypeParser).FullName).Unwrap(); // dynamic works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // casting fails parser = (TypeParser)objparser; So clearly a TypeParser type is coming back, but nevertheless it's not the right one. Hmmm… mysterious.Another couple of tries reveal the problem however:// works dynamic dynParser = objparser; string info = dynParser.GetVersionInfo(); // method call works // c:\wwapps\wwhelp\wwReflection20.dll (Current Execution Folder) string info3 = typeof(TypeParser).Assembly.CodeBase; // c:\program files\vfp9\wwReflection20.dll (my COM client EXE's folder) string info4 = dynParser.GetType().Assembly.CodeBase; // fails parser = (TypeParser)objparser; As you can see the second value is coming from a totally different assembly. Note that this is even though I EXPLICITLY SPECIFIED an assembly path to load the assembly from! Instead .NET decided to load the assembly from the original ApplicationBase folder. Ouch! How I actually tracked this down was a little more tedious: I added a method like this to both the factory and the instance types and then compared notes:public string GetVersionInfo() { return ".NET Version: " + Environment.Version.ToString() + "\r\n" + "wwReflection Assembly: " + typeof(TypeParserFactory).Assembly.CodeBase.Replace("file:///", "").Replace("/", "\\") + "\r\n" + "Assembly Cur Dir: " + Directory.GetCurrentDirectory() + "\r\n" + "ApplicationBase: " + AppDomain.CurrentDomain.SetupInformation.ApplicationBase + "\r\n" + "App Domain: " + AppDomain.CurrentDomain.FriendlyName + "\r\n"; } For the factory I got: .NET Version: 4.0.30319.239wwReflection Assembly: c:\wwapps\wwhelp\bin\wwreflection20.dllAssembly Cur Dir: c:\wwapps\wwhelpApplicationBase: C:\Programs\vfp9\App Domain: wwReflection534cfa1f For the instance type I got: .NET Version: 4.0.30319.239wwReflection Assembly: C:\\Programs\\vfp9\wwreflection20.dllAssembly Cur Dir: c:\\wwapps\\wwhelpApplicationBase: C:\\Programs\\vfp9\App Domain: wwDotNetBridge_56006605 which clearly shows the problem. You can see that both are loading from different appDomains but the each is loading the assembly from a different location. Probably a better solution yet (for ANY kind of assembly loading problem) is to use the .NET Fusion Log Viewer to trace assembly loads.The Fusion viewer will show a load trace for each assembly loaded and where it's looking to find it. Here's what the viewer looks like: The last trace above that I found for the second wwReflection20 load (the one that is wonky) looks like this:*** Assembly Binder Log Entry (1/13/2012 @ 3:06:49 AM) *** The operation was successful. Bind result: hr = 0x0. The operation completed successfully. Assembly manager loaded from: C:\Windows\Microsoft.NET\Framework\V4.0.30319\clr.dll Running under executable c:\programs\vfp9\vfp9.exe --- A detailed error log follows. === Pre-bind state information === LOG: User = Ras\ricks LOG: DisplayName = wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null (Fully-specified) LOG: Appbase = file:///C:/Programs/vfp9/ LOG: Initial PrivatePath = NULL LOG: Dynamic Base = NULL LOG: Cache Base = NULL LOG: AppName = vfp9.exe Calling assembly : (Unknown). === LOG: This bind starts in default load context. LOG: Using application configuration file: C:\Programs\vfp9\vfp9.exe.Config LOG: Using host configuration file: LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework\V4.0.30319\config\machine.config. LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind). LOG: Attempting download of new URL file:///C:/Programs/vfp9/wwReflection20.DLL. LOG: Assembly download was successful. Attempting setup of file: C:\Programs\vfp9\wwReflection20.dll LOG: Entering run-from-source setup phase. LOG: Assembly Name is: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null LOG: Binding succeeds. Returns assembly from C:\Programs\vfp9\wwReflection20.dll. LOG: Assembly is loaded in default load context. WRN: The same assembly was loaded into multiple contexts of an application domain: WRN: Context: Default | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: Context: LoadFrom | Domain ID: 2 | Assembly Name: wwReflection20, Version=4.61.0.0, Culture=neutral, PublicKeyToken=null WRN: This might lead to runtime failures. WRN: It is recommended to inspect your application on whether this is intentional or not. WRN: See whitepaper http://go.microsoft.com/fwlink/?LinkId=109270 for more information and common solutions to this issue. Notice that the fusion log clearly shows that the .NET loader makes no attempt to even load the assembly from the path I explicitly specified. Remember your Assembly Locations As mentioned earlier all failures I've seen like this ultimately resulted from different versions of the same type being available in the two AppDomains. At first sight that seems ridiculous - how could the types be different and why would you have multiple assemblies - but there are actually a number of scenarios where it's quite possible to have multiple copies of the same assembly floating around in multiple places. If you're hosting different environments (like hosting the Razor Engine, or ASP.NET Runtime for example) it's common to create a private BIN folder and it's important to make sure that there's no overlap of assemblies. In my case of Html Help Builder the problem started because I'm using COM interop to access the .NET assembly and the above code. COM Interop has very specific requirements on where assemblies can be found and because I was mucking around with the loader code today, I ended up moving assemblies around to a new location for explicit loading. The explicit load works in the main AppDomain, but failed in the remote domain as I showed. The solution here was simple enough: Delete the extraneous assembly which was left around by accident. Not a common problem, but one that when it bites is pretty nasty to figure out because it seems so unlikely that types wouldn't match. I know I've run into this a few times and writing this down hopefully will make me remember in the future rather than poking around again for an hour trying to debug the issue as I did today. Hopefully it'll save some of you some time as well in the future.© Rick Strahl, West Wind Technologies, 2005-2012Posted in .NET  COM   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• How to write a generic service in WCF

  - by rezaxp

  In one of my recent projects I needed a generic service as a facade to handle General activities such as CRUD.Therefor I searched as Many as I could but there was no Idea on generic services so I tried to figure it out by my self.Finally,I found a way :Create a generic contract as below :[ServiceContract] public interface IEntityReadService<TEntity>         where TEntity : EntityBase, new()     {         [OperationContract(Name = "Get")]         TEntity Get(Int64 Id);         [OperationContract(Name = "GetAll")]         List<TEntity> GetAll();         [OperationContract(Name = "GetAllPaged")]         List<TEntity> GetAll(int pageSize, int currentPageIndex, ref int totalRecords);         List<TEntity> GetAll(string whereClause, string orderBy, int pageSize, int currentPageIndex, ref int totalRecords);            }then create your service class :  public class GenericService<TEntity> :IEntityReadService<TEntity> where TEntity : EntityBase, new() {#region Implementation of IEntityReadService<TEntity>         public TEntity Get(long Id)         {             return BusinessController.Get(Id);         }         public List<TEntity> GetAll()         {             try             {                 return BusinessController.GetAll().ToList();             }             catch (Exception ex)             {                                  throw;             }                      }         public List<TEntity> GetAll(int pageSize, int currentPageIndex, ref int totalRecords)         {             return                 BusinessController.GetAll(pageSize, currentPageIndex, ref totalRecords).ToList();         }         public List<TEntity> GetAll(string whereClause, string orderBy, int pageSize, int currentPageIndex, ref int totalRecords)         {             return                 BusinessController.GetAll(pageSize, currentPageIndex, ref totalRecords, whereClause, orderBy).ToList();         }         #endregion} Then, set your EndPoint configuration in this way :<endpoint address="myAddress" binding="basicHttpBinding" bindingConfiguration="myBindingConfiguration1" contract="Contracts.IEntityReadService`1[[Entities.mySampleEntity, Entities]], Service.Contracts" />

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• How do you keep code with continuations/callbacks readable?

  - by Heinzi

  Summary: Are there some well-established best-practice patterns that I can follow to keep my code readable in spite of using asynchronous code and callbacks? I'm using a JavaScript library that does a lot of stuff asynchronously and heavily relies on callbacks. It seems that writing a simple "load A, load B, ..." method becomes quite complicated and hard to follow using this pattern. Let me give a (contrived) example. Let's say I want to load a bunch of images (asynchronously) from a remote web server. In C#/async, I'd write something like this: disableStartButton(); foreach (myData in myRepository) { var result = await LoadImageAsync("http://my/server/GetImage?" + myData.Id); if (result.Success) { myData.Image = result.Data; } else { write("error loading Image " + myData.Id); return; } } write("success"); enableStartButton(); The code layout follows the "flow of events": First, the start button is disabled, then the images are loaded (await ensures that the UI stays responsive) and then the start button is enabled again. In JavaScript, using callbacks, I came up with this: disableStartButton(); var count = myRepository.length; function loadImage(i) { if (i >= count) { write("success"); enableStartButton(); return; } myData = myRepository[i]; LoadImageAsync("http://my/server/GetImage?" + myData.Id, function(success, data) { if (success) { myData.Image = data; } else { write("error loading image " + myData.Id); return; } loadImage(i+1); } ); } loadImage(0); I think the drawbacks are obvious: I had to rework the loop into a recursive call, the code that's supposed to be executed in the end is somewhere in the middle of the function, the code starting the download (loadImage(0)) is at the very bottom, and it's generally much harder to read and follow. It's ugly and I don't like it. I'm sure that I'm not the first one to encounter this problem, so my question is: Are there some well-established best-practice patterns that I can follow to keep my code readable in spite of using asynchronous code and callbacks?

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• How should I design my database API commands? [closed]

  - by WebDev

  I am developing a database API for a project, with commands for getting data from the database. For example, I have one gib table, so the command for that is: getgib name alias limit fields If the user pass their name: getgib rahul Then it will return all gib data whose name is like rahul. If an alias is given then it will return all the gib owned by the user whose alias (userid) was given. I want to design the commands: limit: to limit the record in query, fields: extra fields I want to add in the select query. So now the commands are set, but: I want the gibs by the gibid, so how to make this or any suggestion to improve my command is welcome. If the user doesn't want to specify the name, and he wants only the gibs by providing alias, then what separator should I use instead of name?

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• Returning a mock object from a mock object

  - by Songo

  I'm trying to return an object when mocking a parser class. This is the test code using PHPUnit 3.7 //set up the result object that I want to be returned from the call to parse method $parserResult= new ParserResult(); $parserResult->setSegment('some string'); //set up the stub Parser object $stubParser=$this->getMock('Parser'); $stubParser->expects($this->any()) ->method('parse') ->will($this->returnValue($parserResult)); //injecting the stub to my client class $fileHeaderParser= new FileWriter($stubParser); $output=$fileParser->writeStringToFile(); Inside my writeStringToFile() method I'm using $parserResult like this: writeStringToFile(){ //Some code... $parserResult=$parser->parse(); $segment=$parserResult->getSegment();//that's why I set the segment in the test. } Should I mock ParserResult in the first place, so that the mock returns a mock? Is it good design for mocks to return mocks? Is there a better approach to do this all?!

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• PHP MVC error handling, view display and user permissions

  - by cen

  I am building a moderation panel from scratch in a MVC approach and a lot of questions cropped up during development. I would like to hear from others how they handle these situations. Error handling Should you handle an error inside the class method or should the method return something anyway and you handle the error in controller? What about PDO exceptions, how to handle them? For example, let's say we have a method that returns true if the user exists in a table and false if he does not exist. What do you return in the catch statement? You can't just return false because then the controller assumes that everything is alright while the truth is that something must be seriously broken. Displaying the error from the method completely breaks the whole design. Maybe a page redirect inside the method? The proper way to show a view The controller right now looks something like this: include('view/header.php'); if ($_GET['m']=='something') include('view/something.php'); elseif ($_GET['m']=='somethingelse') include('view/somethingelse.php'); include('view/foter.php'); Each view also checks if it was included from the index page to prevent it being accessed directly. There is a view file for each different document body. Is this way of including different views ok or is there a more proper way? Managing user rights Each user has his own rights, what he can see and what he can do. Which part of the system should verify that user has the permission to see the view, controller or view itself? Right now I do permission checks directly in the view because each view can contain several forms that require different permissions and I would need to make a seperate file for each of them if it was put in the controller. I also have to re-check for the permissions everytime a form is submitted because form data can be easily forged. The truth is, all this permission checking and validating the inputs just turns the controller into a huge if/then/else cluster. I feel like 90% of the time I am doing error checks/permissions/validations and very little of the actual logic. Is this normal even for popular frameworks?

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• Can a loosely typed language be considered true object oriented?

  - by user61852

  Can a loosely typed programming language like PHP be really considered object oriented? I mean, the methods don't have returning types and method parameters has no declared type either. Doesn't class design require methods to have a return type? Don't methods signatures have specifically-typed parameters? How can OOP techniques help you code in PHP if you always have to check the types of parameters received because the language doesn't enforce types? Please, if I'm wrong, explain it to me. When you design things using UML, then code classes in PHP with no return-typed methods and no-type parameters... Is the code really compliant with the UML design? You spend time designing the architecture of your software, then the compiler doesn't force the programmer to follow your design while coding, letting he/she assign any object variable to any other variable with no "type-mismatch" warning.

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• A Closable jQuery Plug-in

  - by Rick Strahl

  In my client side development I deal a lot with content that pops over the main page. Be it data entry ‘windows’ or dialogs or simple pop up notes. In most cases this behavior goes with draggable windows, but sometimes it’s also useful to have closable behavior on static page content that the user can choose to hide or otherwise make invisible or fade out. Here’s a small jQuery plug-in that provides .closable() behavior to most elements by using either an image that is provided or – more appropriately by using a CSS class to define the picture box layout. /* * * Closable * * Makes selected DOM elements closable by making them * invisible when close icon is clicked * * Version 1.01 * @requires jQuery v1.3 or later * * Copyright (c) 2007-2010 Rick Strahl * http://www.west-wind.com/ * * Licensed under the MIT license: * http://www.opensource.org/licenses/mit-license.php Support CSS: .closebox { position: absolute; right: 4px; top: 4px; background-image: url(images/close.gif); background-repeat: no-repeat; width: 14px; height: 14px; cursor: pointer; opacity: 0.60; filter: alpha(opacity="80"); } .closebox:hover { opacity: 0.95; filter: alpha(opacity="100"); } Options: * handle Element to place closebox into (like say a header). Use if main element and closebox container are two different elements. * closeHandler Function called when the close box is clicked. Return true to close the box return false to keep it visible. * cssClass The CSS class to apply to the close box DIV or IMG tag. * imageUrl Allows you to specify an explicit IMG url that displays the close icon. If used bypasses CSS image styling. * fadeOut Optional provide fadeOut speed. Default no fade out occurs */ (function ($) { $.fn.closable = function (options) { var opt = { handle: null, closeHandler: null, cssClass: "closebox", imageUrl: null, fadeOut: null }; $.extend(opt, options); return this.each(function (i) { var el = $(this); var pos = el.css("position"); if (!pos || pos == "static") el.css("position", "relative"); var h = opt.handle ? $(opt.handle).css({ position: "relative" }) : el; var div = opt.imageUrl ? $("<img>").attr("src", opt.imageUrl).css("cursor", "pointer") : $("<div>"); div.addClass(opt.cssClass) .click(function (e) { if (opt.closeHandler) if (!opt.closeHandler.call(this, e)) return; if (opt.fadeOut) $(el).fadeOut(opt.fadeOut); else $(el).hide(); }); if (opt.imageUrl) div.css("background-image", "none"); h.append(div); }); } })(jQuery); The plugin can be applied against any selector that is a container (typically a div tag). The close image or close box is provided typically by way of a CssClass - .closebox by default – which supplies the image as part of the CSS styling. The default styling for the box looks something like this: .closebox { position: absolute; right: 4px; top: 4px; background-image: url(images/close.gif); background-repeat: no-repeat; width: 14px; height: 14px; cursor: pointer; opacity: 0.60; filter: alpha(opacity="80"); } .closebox:hover { opacity: 0.95; filter: alpha(opacity="100"); } Alternately you can also supply an image URL which overrides the background image in the style sheet. I use this plug-in mostly on pop up windows that can be closed, but it’s also quite handy for remove/delete behavior in list displays like this: you can find this sample here to look to play along: http://www.west-wind.com/WestwindWebToolkit/Samples/Ajax/AmazonBooks/BooksAdmin.aspx For closable windows it’s nice to have something reusable because in my client framework there are lots of different kinds of windows that can be created: Draggables, Modal Dialogs, HoverPanels etc. and they all use the client .closable plug-in to provide the closable operation in the same way with a few options. Plug-ins are great for this sort of thing because they can also be aggregated and so different components can pick and choose the behavior they want. The window here is a draggable, that’s closable and has shadow behavior and the server control can simply generate the appropriate plug-ins to apply to the main <div> tag: $().ready(function() { $('#ctl00_MainContent_panEditBook') .closable({ handle: $('#divEditBook_Header') }) .draggable({ dragDelay: 100, handle: '#divEditBook_Header' }) .shadow({ opacity: 0.25, offset: 6 }); }) The window is using the default .closebox style and has its handle set to the header bar (Book Information). The window is just closable to go away so no event handler is applied. Actually I cheated – the actual page’s .closable is a bit more ugly in the sample as it uses an image from a resources file: .closable({ imageUrl: '/WestWindWebToolkit/Samples/WebResource.axd?d=TooLongAndNastyToPrint', handle: $('#divEditBook_Header')}) so you can see how to apply a custom image, which in this case is generated by the server control wrapping the client DragPanel. More interesting maybe is to apply the .closable behavior to list scenarios. For example, each of the individual items in the list display also are .closable using this plug-in. Rather than having to define each item with Html for an image, event handler and link, when the client template is rendered the closable behavior is attached to the list. Here I’m using client-templating and the code that this is done with looks like this: function loadBooks() { showProgress(); // Clear the content $("#divBookListWrapper").empty(); var filter = $("#" + scriptVars.lstFiltersId).val(); Proxy.GetBooks(filter, function(books) { $(books).each(function(i) { updateBook(this); showProgress(true); }); }, onPageError); } function updateBook(book,highlight) { // try to retrieve the single item in the list by tag attribute id var item = $(".bookitem[tag=" +book.Pk +"]"); // grab and evaluate the template var html = parseTemplate(template, book); var newItem = $(html) .attr("tag", book.Pk.toString()) .click(function() { var pk = $(this).attr("tag"); editBook(this, parseInt(pk)); }) .closable({ closeHandler: function(e) { removeBook(this, e); }, imageUrl: "../../images/remove.gif" }); if (item.length > 0) item.after(newItem).remove(); else newItem.appendTo($("#divBookListWrapper")); if (highlight) { newItem .addClass("pulse") .effect("bounce", { distance: 15, times: 3 }, 400); setTimeout(function() { newItem.removeClass("pulse"); }, 1200); } } Here the closable behavior is applied to each of the items along with an event handler, which is nice and easy compared to having to embed the right HTML and click handling into each item in the list individually via markup. Ideally though (and these posts make me realize this often a little late) I probably should set up a custom cssClass to handle the rendering – maybe a CSS class called .removebox that only changes the image from the default box image. This example also hooks up an event handler that is fired in response to the close. In the list I need to know when the remove button is clicked so I can fire of a service call to the server to actually remove the item from the database. The handler code can also return false; to indicate that the window should not be closed optionally. Returning true will close the window. You can find more information about the .closable class behavior and options here: .closable Documentation Plug-ins make Server Control JavaScript much easier I find this plug-in immensely useful especial as part of server control code, because it simplifies the code that has to be generated server side tremendously. This is true of plug-ins in general which make it so much easier to create simple server code that only generates plug-in options, rather than full blocks of JavaScript code.  For example, here’s the relevant code from the DragPanel server control which generates the .closable() behavior: if (this.Closable && !string.IsNullOrEmpty(DragHandleID) ) { string imageUrl = this.CloseBoxImage; if (imageUrl == "WebResource" ) imageUrl = ScriptProxy.GetWebResourceUrl(this, this.GetType(), ControlResources.CLOSE_ICON_RESOURCE); StringBuilder closableOptions = new StringBuilder("imageUrl: '" + imageUrl + "'"); if (!string.IsNullOrEmpty(this.DragHandleID)) closableOptions.Append(",handle: $('#" + this.DragHandleID + "')"); if (!string.IsNullOrEmpty(this.ClientDialogHandler)) closableOptions.Append(",handler: " + this.ClientDialogHandler); if (this.FadeOnClose) closableOptions.Append(",fadeOut: 'slow'"); startupScript.Append(@" .closable({ " + closableOptions + "})"); } The same sort of block is then used for .draggable and .shadow which simply sets options. Compared to the code I used to have in pre-jQuery versions of my JavaScript toolkit this is a walk in the park. In those days there was a bunch of JS generation which was ugly to say the least. I know a lot of folks frown on using server controls, especially the UI is client centric as the example is. However, I do feel that server controls can greatly simplify the process of getting the right behavior attached more easily and with the help of IntelliSense. Often the script markup is easier is especially if you are dealing with complex, multiple plug-in associations that often express more easily with property values on a control. Regardless of whether server controls are your thing or not this plug-in can be useful in many scenarios. Even in simple client-only scenarios using a plug-in with a few simple parameters is nicer and more consistent than creating the HTML markup over and over again. I hope some of you find this even a small bit as useful as I have. Related Links Download jquery.closable West Wind Web Toolkit jQuery Plug-ins © Rick Strahl, West Wind Technologies, 2005-2010Posted in jQuery   ASP.NET  JavaScript  

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• A really simple ViewModel base class with strongly-typed INotifyPropertyChanged

  - by Daniel Cazzulino

  I have already written about other alternative ways of implementing INotifyPropertyChanged, as well as augment your view models with a bit of automatic code generation for the same purpose. But for some co-workers, either one seemed a bit too much :o). So, back on the drawing board, we came up with the following view model authoring experience:public class MyViewModel : ViewModel, IExplicitInterface { private int value; public int Value { get { return value; } set { this.value = value; RaiseChanged(() =&gt; this.Value); } } double IExplicitInterface.DoubleValue { get { return value; } set { this.value = (int)value; RaiseChanged(() =&gt; ((IExplicitInterface)this).DoubleValue); } } } ...Read full article

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• Equal Gifts Algorithm Problem

  - by 7Aces

  Problem Link - http://opc.iarcs.org.in/index.php/problems/EQGIFTS It is Lavanya's birthday and several families have been invited for the birthday party. As is customary, all of them have brought gifts for Lavanya as well as her brother Nikhil. Since their friends are all of the erudite kind, everyone has brought a pair of books. Unfortunately, the gift givers did not clearly indicate which book in the pair is for Lavanya and which one is for Nikhil. Now it is up to their father to divide up these books between them. He has decided that from each of these pairs, one book will go to Lavanya and one to Nikhil. Moreover, since Nikhil is quite a keen observer of the value of gifts, the books have to be divided in such a manner that the total value of the books for Lavanya is as close as possible to total value of the books for Nikhil. Since Lavanya and Nikhil are kids, no book that has been gifted will have a value higher than 300 Rupees... For the problem, I couldn't think of anything except recursion. The code I wrote is given below. But the problem is that the code is time-inefficient and gives TLE (Time Limit Exceeded) for 9 out of 10 test cases! What would be a better approach to the problem? Code - #include<cstdio> #include<climits> #include<algorithm> using namespace std; int n,g[150][2]; int diff(int a,int b,int f) { ++f; if(f==n) { if(a>b) { return a-b; } else { return b-a; } } return min(diff(a+g[f][0],b+g[f][1],f),diff(a+g[f][1],b+g[f][0],f)); } int main() { int i; scanf("%d",&n); for(i=0;i<n;++i) { scanf("%d%d",&g[i][0],&g[i][1]); } printf("%d",diff(g[0][0],g[0][1],0)); } Note - It is just a practice question, & is not part of a competition.

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• 2D OBB collision detection, resolving collisions?

  - by Milo

  I currently use OBBs and I have a vehicle that is a rigid body and some buildings. Here is my update() private void update() { camera.setPosition((vehicle.getPosition().x * camera.getScale()) - ((getWidth() ) / 2.0f), (vehicle.getPosition().y * camera.getScale()) - ((getHeight() ) / 2.0f)); //camera.move(input.getAnalogStick().getStickValueX() * 15.0f, input.getAnalogStick().getStickValueY() * 15.0f); if(input.isPressed(ControlButton.BUTTON_GAS)) { vehicle.setThrottle(1.0f, false); } if(input.isPressed(ControlButton.BUTTON_BRAKE)) { vehicle.setBrakes(1.0f); } vehicle.setSteering(input.getAnalogStick().getStickValueX()); vehicle.update(16.6666f / 1000.0f); ArrayList<Building> buildings = city.getBuildings(); for(Building b : buildings) { if(vehicle.getRect().overlaps(b.getRect())) { vehicle.update(-17.0f / 1000.0f); break; } } } The collision detection works well. What doesn't is how they are dealt with. My goal is simple. If the vehicle hits a building, it should stop, and never go into the building. When I apply negative torque to reverse the car should not feel buggy and move away from the building. I don't want this to look buggy. This is my rigid body class: class RigidBody extends Entity { //linear private Vector2D velocity = new Vector2D(); private Vector2D forces = new Vector2D(); private float mass; //angular private float angularVelocity; private float torque; private float inertia; //graphical private Vector2D halfSize = new Vector2D(); private Bitmap image; public RigidBody() { //set these defaults so we don't get divide by zeros mass = 1.0f; inertia = 1.0f; } //intialize out parameters public void initialize(Vector2D halfSize, float mass, Bitmap bitmap) { //store physical parameters this.halfSize = halfSize; this.mass = mass; image = bitmap; inertia = (1.0f / 20.0f) * (halfSize.x * halfSize.x) * (halfSize.y * halfSize.y) * mass; RectF rect = new RectF(); float scalar = 10.0f; rect.left = (int)-halfSize.x * scalar; rect.top = (int)-halfSize.y * scalar; rect.right = rect.left + (int)(halfSize.x * 2.0f * scalar); rect.bottom = rect.top + (int)(halfSize.y * 2.0f * scalar); setRect(rect); } public void setLocation(Vector2D position, float angle) { getRect().set(position, getWidth(), getHeight(), angle); } public Vector2D getPosition() { return getRect().getCenter(); } @Override public void update(float timeStep) { //integrate physics //linear Vector2D acceleration = Vector2D.scalarDivide(forces, mass); velocity = Vector2D.add(velocity, Vector2D.scalarMultiply(acceleration, timeStep)); Vector2D c = getRect().getCenter(); c = Vector2D.add(getRect().getCenter(), Vector2D.scalarMultiply(velocity , timeStep)); setCenter(c.x, c.y); forces = new Vector2D(0,0); //clear forces //angular float angAcc = torque / inertia; angularVelocity += angAcc * timeStep; setAngle(getAngle() + angularVelocity * timeStep); torque = 0; //clear torque } //take a relative Vector2D and make it a world Vector2D public Vector2D relativeToWorld(Vector2D relative) { Matrix mat = new Matrix(); float[] Vector2Ds = new float[2]; Vector2Ds[0] = relative.x; Vector2Ds[1] = relative.y; mat.postRotate(JMath.radToDeg(getAngle())); mat.mapVectors(Vector2Ds); return new Vector2D(Vector2Ds[0], Vector2Ds[1]); } //take a world Vector2D and make it a relative Vector2D public Vector2D worldToRelative(Vector2D world) { Matrix mat = new Matrix(); float[] Vectors = new float[2]; Vectors[0] = world.x; Vectors[1] = world.y; mat.postRotate(JMath.radToDeg(-getAngle())); mat.mapVectors(Vectors); return new Vector2D(Vectors[0], Vectors[1]); } //velocity of a point on body public Vector2D pointVelocity(Vector2D worldOffset) { Vector2D tangent = new Vector2D(-worldOffset.y, worldOffset.x); return Vector2D.add( Vector2D.scalarMultiply(tangent, angularVelocity) , velocity); } public void applyForce(Vector2D worldForce, Vector2D worldOffset) { //add linear force forces = Vector2D.add(forces ,worldForce); //add associated torque torque += Vector2D.cross(worldOffset, worldForce); } @Override public void draw( GraphicsContext c) { c.drawRotatedScaledBitmap(image, getPosition().x, getPosition().y, getWidth(), getHeight(), getAngle()); } } Essentially, when any rigid body hits a building it should exhibit the same behavior. How is collision solving usually done? Thanks

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• InvokeRequired not reliable?

  - by marocanu2001

  InvalidOperationException: Cross-thread operation not valid: Control 'progressBar' accessed from a thread other than the thread it was created ... Now this is not a nice way to start a day! not even if it's a Monday! So you have seen this and already thought, come on, this is an old one, just ask whether InvokeRequired before calling the method in the control, something like this: if (progressBar.InvokeRequired) {           progressBar.Invoke  ( new MethodInvoker( delegate {  progressBar.Value = 50;    }) ) }else      progressBar.Value = 50;    Unfortunately this was not working the way I would have expected, I got this error, debugged and though in debugging the InvokeRequired had become true , the error was thrown on the branch that did not required Invoke. So there was a scenario where InvokeRequired returned false and still accessing the control was not on the right thread ... Problem was that I kept showing and hiding the little form showing the progressbar. The progressbar was updating on an event  , ProgressChanged and I could not guarantee the little form was loaded by the time the event was thrown. So , spotted the problem, if none of the parents of the control you try to modify is created at the time of the method invoking, the InvokeRequired returns true! That causes your code to execute on the woring thread. Of course, updating UI before the win dow was created is not a legitimate action either, still I would have expected a different error. MSDN: "If the control's handle does not yet exist, InvokeRequired searches up the control's parent chain until it finds a control or form that does have a window handle. If no appropriate handle can be found, the InvokeRequired method returns false. This means that InvokeRequired can return false if Invoke is not required (the call occurs on the same thread), or if the control was created on a different thread but the control's handle has not yet been created." Have  a look at InvokeRequired's implementation: public bool InvokeRequired {     get     {         HandleRef hWnd;         int lpdwProcessId;         if (this.IsHandleCreated)         {             hWnd = new HandleRef(this, this.Handle);         }         else         {             Control wrapper = this.FindMarshallingControl();             if (!wrapper.IsHandleCreated)             {                 return false; // <==========             }             hWnd = new HandleRef(wrapper, wrapper.Handle);         }         int windowThreadProcessId = SafeNativeMethods.GetWindowThreadProcessId(hWnd, out lpdwProcessId);         int currentThreadId = SafeNativeMethods.GetCurrentThreadId();         return (windowThreadProcessId != currentThreadId);     } } Here 's a good article about this and a workaround http://www.ikriv.com/en/prog/info/dotnet/MysteriousHang.html

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• Normal maps red in OpenGL?

  - by KaiserJohaan

  I am using Assimp to import 3d models, and FreeImage to parse textures. The problem I am having is that the normal maps are actually red rather than blue when I try to render them as normal diffuse textures. http://i42.tinypic.com/289ing3.png When I open the images in a image-viewing program they do indeed show up as blue. Heres when I create the texture; OpenGLTexture::OpenGLTexture(const std::vector<uint8_t>& textureData, uint32_t textureWidth, uint32_t textureHeight, TextureType textureType, Logger& logger) : mLogger(logger), mTextureID(gNextTextureID++), mTextureType(textureType) { glGenTextures(1, &mTexture); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, mTexture); CHECK_GL_ERROR(mLogger); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureWidth, textureHeight, 0, glTextureFormat, GL_UNSIGNED_BYTE, &textureData[0]); CHECK_GL_ERROR(mLogger); glGenerateMipmap(GL_TEXTURE_2D); CHECK_GL_ERROR(mLogger); glBindTexture(GL_TEXTURE_2D, 0); CHECK_GL_ERROR(mLogger); } Here is my fragment shader. You can see I just commented out the normal-map parsing and treated the normal map texture as the diffuse texture to display it and illustrate the problem. As for the rest of the code it interacts as expected with the diffuse textures so I dont see a obvious problem there. "#version 330 \n \ \n \ layout(std140) uniform; \n \ \n \ const int MAX_LIGHTS = 8; \n \ \n \ struct Light \n \ { \n \ vec4 mLightColor; \n \ vec4 mLightPosition; \n \ vec4 mLightDirection; \n \ \n \ int mLightType; \n \ float mLightIntensity; \n \ float mLightRadius; \n \ float mMaxDistance; \n \ }; \n \ \n \ uniform UnifLighting \n \ { \n \ vec4 mGamma; \n \ vec3 mViewDirection; \n \ int mNumLights; \n \ \n \ Light mLights[MAX_LIGHTS]; \n \ } Lighting; \n \ \n \ uniform UnifMaterial \n \ { \n \ vec4 mDiffuseColor; \n \ vec4 mAmbientColor; \n \ vec4 mSpecularColor; \n \ vec4 mEmissiveColor; \n \ \n \ bool mHasDiffuseTexture; \n \ bool mHasNormalTexture; \n \ bool mLightingEnabled; \n \ float mSpecularShininess; \n \ } Material; \n \ \n \ uniform sampler2D unifDiffuseTexture; \n \ uniform sampler2D unifNormalTexture; \n \ \n \ in vec3 frag_position; \n \ in vec3 frag_normal; \n \ in vec2 frag_texcoord; \n \ in vec3 frag_tangent; \n \ in vec3 frag_bitangent; \n \ \n \ out vec4 finalColor; " " \n \ \n \ void CalcGaussianSpecular(in vec3 dirToLight, in vec3 normal, out float gaussianTerm) \n \ { \n \ vec3 viewDirection = normalize(Lighting.mViewDirection); \n \ vec3 halfAngle = normalize(dirToLight + viewDirection); \n \ \n \ float angleNormalHalf = acos(dot(halfAngle, normalize(normal))); \n \ float exponent = angleNormalHalf / Material.mSpecularShininess; \n \ exponent = -(exponent * exponent); \n \ \n \ gaussianTerm = exp(exponent); \n \ } \n \ \n \ vec4 CalculateLighting(in Light light, in vec4 diffuseTexture, in vec3 normal) \n \ { \n \ if (light.mLightType == 1) // point light \n \ { \n \ vec3 positionDiff = light.mLightPosition.xyz - frag_position; \n \ float dist = max(length(positionDiff) - light.mLightRadius, 0); \n \ \n \ float attenuation = 1 / ((dist/light.mLightRadius + 1) * (dist/light.mLightRadius + 1)); \n \ attenuation = max((attenuation - light.mMaxDistance) / (1 - light.mMaxDistance), 0); \n \ \n \ vec3 dirToLight = normalize(positionDiff); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (attenuation * angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (attenuation * gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 2) // directional light \n \ { \n \ vec3 dirToLight = normalize(light.mLightDirection.xyz); \n \ float angleNormal = clamp(dot(normalize(normal), dirToLight), 0, 1); \n \ \n \ float gaussianTerm = 0.0; \n \ if (angleNormal > 0.0) \n \ CalcGaussianSpecular(dirToLight, normal, gaussianTerm); \n \ \n \ return diffuseTexture * (angleNormal * Material.mDiffuseColor * light.mLightIntensity * light.mLightColor) + \n \ (gaussianTerm * Material.mSpecularColor * light.mLightIntensity * light.mLightColor); \n \ } \n \ else if (light.mLightType == 4) // ambient light \n \ return diffuseTexture * Material.mAmbientColor * light.mLightIntensity * light.mLightColor; \n \ else \n \ return vec4(0.0); \n \ } \n \ \n \ void main() \n \ { \n \ vec4 diffuseTexture = vec4(1.0); \n \ if (Material.mHasDiffuseTexture) \n \ diffuseTexture = texture(unifDiffuseTexture, frag_texcoord); \n \ \n \ vec3 normal = frag_normal; \n \ if (Material.mHasNormalTexture) \n \ { \n \ diffuseTexture = vec4(normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0), 1.0); \n \ // vec3 normalTangentSpace = normalize(texture(unifNormalTexture, frag_texcoord).xyz * 2.0 - 1.0); \n \ //mat3 tangentToWorldSpace = mat3(normalize(frag_tangent), normalize(frag_bitangent), normalize(frag_normal)); \n \ \n \ // normal = tangentToWorldSpace * normalTangentSpace; \n \ } \n \ \n \ if (Material.mLightingEnabled) \n \ { \n \ vec4 accumLighting = vec4(0.0); \n \ \n \ for (int lightIndex = 0; lightIndex < Lighting.mNumLights; lightIndex++) \n \ accumLighting += Material.mEmissiveColor * diffuseTexture + \n \ CalculateLighting(Lighting.mLights[lightIndex], diffuseTexture, normal); \n \ \n \ finalColor = pow(accumLighting, Lighting.mGamma); \n \ } \n \ else { \n \ finalColor = pow(diffuseTexture, Lighting.mGamma); \n \ } \n \ } \n"; Why is this? does normal-map textures need some sort of special treatment in opengl?

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• C# async and actors

  - by Alex.Davies

  If you read my last post about async, you might be wondering what drove me to write such odd code in the first place. The short answer is that .NET Demon is written using NAct Actors. Actors are an old idea, which I believe deserve a renaissance under C# 5. The idea is to isolate each stateful object so that only one thread has access to its state at any point in time. That much should be familiar, it's equivalent to traditional lock-based synchronization. The different part is that actors pass "messages" to each other rather than calling a method and waiting for it to return. By doing that, each thread can only ever be holding one lock. This completely eliminates deadlocks, my least favourite concurrency problem. Most people who use actors take this quite literally, and there are plenty of frameworks which help you to create message classes and loops which can receive the messages, inspect what type of message they are, and process them accordingly. But I write C# for a reason. Do I really have to choose between using actors and everything I love about object orientation in C#? Type safety Interfaces Inheritance Generics As it turns out, no. You don't need to choose between messages and method calls. A method call makes a perfectly good message, as long as you don't wait for it to return. This is where asynchonous methods come in. I have used NAct for a while to wrap my objects in a proxy layer. As long as I followed the rule that methods must always return void, NAct queued up the call for later, and immediately released my thread. When I needed to get information out of other actors, I could use EventHandlers and callbacks (continuation passing style, for any CS geeks reading), and NAct would call me back in my isolated thread without blocking the actor that raised the event. Using callbacks looks horrible though. To remind you: m_BuildControl.FilterEnabledForBuilding(    projects,    enabledProjects = m_OutOfDateProjectFinder.FilterNeedsBuilding(        enabledProjects,             newDirtyProjects =             {                 ....... Which is why I'm really happy that NAct now supports async methods. Now, methods are allowed to return Task rather than just void. I can await those methods, and C# 5 will turn the rest of my method into a continuation for me. NAct will run the other method in the other actor's context, but will make sure that when my method resumes, we're back in my context. Neither actor was ever blocked waiting for the other one. Apart from when they were actually busy doing something, they were responsive to concurrent messages from other sources. To be fair, you could use async methods with lock statements to achieve exactly the same thing, but it's ugly. Here's a realistic example of an object that has a queue of data that gets passed to another object to be processed: class QueueProcessor {    private readonly ItemProcessor m_ItemProcessor = ...     private readonly object m_Sync = new object();    private Queue<object> m_DataQueue = ...    private List<object> m_Results = ...     public async Task ProcessOne() {         object data = null;         lock (m_Sync)         {             data = m_DataQueue.Dequeue();         }         var processedData = await m_ItemProcessor.ProcessData(data); lock (m_Sync)         {             m_Results.Add(processedData);         }     } } We needed to write two lock blocks, one to get the data to process, one to store the result. The worrying part is how easily we could have forgotten one of the locks. Compare that to the version using NAct: class QueueProcessorActor : IActor { private readonly ItemProcessor m_ItemProcessor = ... private Queue<object> m_DataQueue = ... private List<object> m_Results = ... public async Task ProcessOne()     {         // We are an actor, it's always thread-safe to access our private fields         var data = m_DataQueue.Dequeue();         var processedData = await m_ItemProcessor.ProcessData(data);         m_Results.Add(processedData);     } } You don't have to explicitly lock anywhere, NAct ensures that your code will only ever run on one thread, because it's an actor. Either way, async is definitely better than traditional synchronous code. Here's a diagram of what a typical synchronous implementation might do: The left side shows what is running on the thread that has the lock required to access the QueueProcessor's data. The red section is where that lock is held, but doesn't need to be. Contrast that with the async version we wrote above: Here, the lock is released in the middle. The QueueProcessor is free to do something else. Most importantly, even if the ItemProcessor sometimes calls the QueueProcessor, they can never deadlock waiting for each other. So I thoroughly recommend you use async for all code that has to wait a while for things. And if you find yourself writing lots of lock statements, think about using actors as well. Using actors and async together really takes the misery out of concurrent programming.

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• Subterranean IL: Exception handler semantics

  - by Simon Cooper

  In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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• How to structure game states in an entity/component-based system

  - by Eva

  I'm making a game designed with the entity-component paradigm that uses systems to communicate between components as explained here. I've reached the point in my development that I need to add game states (such as paused, playing, level start, round start, game over, etc.), but I'm not sure how to do it with my framework. I've looked at this code example on game states which everyone seems to reference, but I don't think it fits with my framework. It seems to have each state handling its own drawing and updating. My framework has a SystemManager that handles all the updating using systems. For example, here's my RenderingSystem class: public class RenderingSystem extends GameSystem { private GameView gameView_; /** * Constructor * Creates a new RenderingSystem. * @param gameManager The game manager. Used to get the game components. */ public RenderingSystem(GameManager gameManager) { super(gameManager); } /** * Method: registerGameView * Registers gameView into the RenderingSystem. * @param gameView The game view registered. */ public void registerGameView(GameView gameView) { gameView_ = gameView; } /** * Method: triggerRender * Adds a repaint call to the event queue for the dirty rectangle. */ public void triggerRender() { Rectangle dirtyRect = new Rectangle(); for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); dirtyRect.add(graphicsComponent.getDirtyRect()); } gameView_.repaint(dirtyRect); } /** * Method: renderGameView * Renders the game objects onto the game view. * @param g The graphics object that draws the game objects. */ public void renderGameView(Graphics g) { for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); if (!graphicsComponent.isVisible()) continue; GraphicsComponent.Shape shape = graphicsComponent.getShape(); BoundsComponent boundsComponent = object.getComponent(BoundsComponent.class); Rectangle bounds = boundsComponent.getBounds(); g.setColor(graphicsComponent.getColor()); if (shape == GraphicsComponent.Shape.RECTANGULAR) { g.fill3DRect(bounds.x, bounds.y, bounds.width, bounds.height, true); } else if (shape == GraphicsComponent.Shape.CIRCULAR) { g.fillOval(bounds.x, bounds.y, bounds.width, bounds.height); } } } /** * Method: getRenderableObjects * @return The renderable game objects. */ private HashSet<GameObject> getRenderableObjects() { return gameManager.getGameObjectManager().getRelevantObjects( getClass()); } } Also all the updating in my game is event-driven. I don't have a loop like theirs that simply updates everything at the same time. I like my framework because it makes it easy to add new GameObjects, but doesn't have the problems some component-based designs encounter when communicating between components. I would hate to chuck it just to get pause to work. Is there a way I can add game states to my game without removing the entity-component design? Does the game state example actually fit my framework, and I'm just missing something? EDIT: I might not have explained my framework well enough. My components are just data. If I was coding in C++, they'd probably be structs. Here's an example of one: public class BoundsComponent implements GameComponent { /** * The position of the game object. */ private Point pos_; /** * The size of the game object. */ private Dimension size_; /** * Constructor * Creates a new BoundsComponent for a game object with initial position * initialPos and initial size initialSize. The position and size combine * to make up the bounds. * @param initialPos The initial position of the game object. * @param initialSize The initial size of the game object. */ public BoundsComponent(Point initialPos, Dimension initialSize) { pos_ = initialPos; size_ = initialSize; } /** * Method: getBounds * @return The bounds of the game object. */ public Rectangle getBounds() { return new Rectangle(pos_, size_); } /** * Method: setPos * Sets the position of the game object to newPos. * @param newPos The value to which the position of the game object is * set. */ public void setPos(Point newPos) { pos_ = newPos; } } My components do not communicate with each other. Systems handle inter-component communication. My systems also do not communicate with each other. They have separate functionality and can easily be kept separate. The MovementSystem doesn't need to know what the RenderingSystem is rendering to move the game objects correctly; it just need to set the right values on the components, so that when the RenderingSystem renders the game objects, it has accurate data. The game state could not be a system, because it needs to interact with the systems rather than the components. It's not setting data; it's determining which functions need to be called. A GameStateComponent wouldn't make sense because all the game objects share one game state. Components are what make up objects and each one is different for each different object. For example, the game objects cannot have the same bounds. They can have overlapping bounds, but if they share a BoundsComponent, they're really the same object. Hopefully, this explanation makes my framework less confusing.

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• How To Get Web Site Thumbnail Image In ASP.NET

  - by SAMIR BHOGAYTA

  Overview One very common requirement of many web applications is to display a thumbnail image of a web site. A typical example is to provide a link to a dynamic website displaying its current thumbnail image, or displaying images of websites with their links as a result of search (I love to see it on Google). Microsoft .NET Framework 2.0 makes it quite easier to do it in a ASP.NET application. Background In order to generate image of a web page, first we need to load the web page to get their html code, and then this html needs to be rendered in a web browser. After that, a screen shot can be taken easily. I think there is no easier way to do this. Before .NET framework 2.0 it was quite difficult to use a web browser in C# or VB.NET because we either have to use COM+ interoperability or third party controls which becomes headache later. WebBrowser control in .NET framework 2.0 In .NET framework 2.0 we have a new Windows Forms WebBrowser control which is a wrapper around old shwdoc.dll. All you really need to do is to drop a WebBrowser control from your Toolbox on your form in .NET framework 2.0. If you have not used WebBrowser control yet, it's quite easy to use and very consistent with other Windows Forms controls. Some important methods of WebBrowser control are. public bool GoBack(); public bool GoForward(); public void GoHome(); public void GoSearch(); public void Navigate(Uri url); public void DrawToBitmap(Bitmap bitmap, Rectangle targetBounds); These methods are self explanatory with their names like Navigate function which redirects browser to provided URL. It also has a number of useful overloads. The DrawToBitmap (inherited from Control) draws the current image of WebBrowser to the provided bitmap. Using WebBrowser control in ASP.NET 2.0 The Solution Let's start to implement the solution which we discussed above. First we will define a static method to get the web site thumbnail image. public static Bitmap GetWebSiteThumbnail(string Url, int BrowserWidth, int BrowserHeight, int ThumbnailWidth, int ThumbnailHeight) { WebsiteThumbnailImage thumbnailGenerator = new WebsiteThumbnailImage(Url, BrowserWidth, BrowserHeight, ThumbnailWidth, ThumbnailHeight); return thumbnailGenerator.GenerateWebSiteThumbnailImage(); } The WebsiteThumbnailImage class will have a public method named GenerateWebSiteThumbnailImage which will generate the website thumbnail image in a separate STA thread and wait for the thread to exit. In this case, I decided to Join method of Thread class to block the initial calling thread until the bitmap is actually available, and then return the generated web site thumbnail. public Bitmap GenerateWebSiteThumbnailImage() { Thread m_thread = new Thread(new ThreadStart(_GenerateWebSiteThumbnailImage)); m_thread.SetApartmentState(ApartmentState.STA); m_thread.Start(); m_thread.Join(); return m_Bitmap; } The _GenerateWebSiteThumbnailImage will create a WebBrowser control object and navigate to the provided Url. We also register for the DocumentCompleted event of the web browser control to take screen shot of the web page. To pass the flow to the other controls we need to perform a method call to Application.DoEvents(); and wait for the completion of the navigation until the browser state changes to Complete in a loop. private void _GenerateWebSiteThumbnailImage() { WebBrowser m_WebBrowser = new WebBrowser(); m_WebBrowser.ScrollBarsEnabled = false; m_WebBrowser.Navigate(m_Url); m_WebBrowser.DocumentCompleted += new WebBrowserDocument CompletedEventHandler(WebBrowser_DocumentCompleted); while (m_WebBrowser.ReadyState != WebBrowserReadyState.Complete) Application.DoEvents(); m_WebBrowser.Dispose(); } The DocumentCompleted event will be fired when the navigation is completed and the browser is ready for screen shot. We will get screen shot using DrawToBitmap method as described previously which will return the bitmap of the web browser. Then the thumbnail image is generated using GetThumbnailImage method of Bitmap class passing it the required thumbnail image width and height. private void WebBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { WebBrowser m_WebBrowser = (WebBrowser)sender; m_WebBrowser.ClientSize = new Size(this.m_BrowserWidth, this.m_BrowserHeight); m_WebBrowser.ScrollBarsEnabled = false; m_Bitmap = new Bitmap(m_WebBrowser.Bounds.Width, m_WebBrowser.Bounds.Height); m_WebBrowser.BringToFront(); m_WebBrowser.DrawToBitmap(m_Bitmap, m_WebBrowser.Bounds); m_Bitmap = (Bitmap)m_Bitmap.GetThumbnailImage(m_ThumbnailWidth, m_ThumbnailHeight, null, IntPtr.Zero); } One more example here : http://www.codeproject.com/KB/aspnet/Website_URL_Screenshot.aspx

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• Extending Currying: Partial Functions in Javascript

  - by kerry

  Last week I posted about function currying in javascript.  This week I am taking it a step further by adding the ability to call partial functions. Suppose we have a graphing application that will pull data via Ajax and perform some calculation to update a graph.  Using a method with the signature ‘updateGraph(id,value)’. To do this, we have do something like this: 1: for(var i=0;i<objects.length;i++) { 2: Ajax.request('/some/data',{id:objects[i].id},function(json) { 3: updateGraph(json.id, json.value); 4: } 5: } This works fine.  But, using this method we need to return the id in the json response from the server.  This works fine, but is not that elegant and increase network traffic. Using partial function currying we can bind the id parameter and add the second parameter later (when returning from the asynchronous call).  To do this, we will need the updated curry method.  I have added support for sending additional parameters at runtime for curried methods. 1: Function.prototype.curry = function(scope) { 2: scope = scope || window 3: var args = []; 4: for (var i=1, len = arguments.length; i < len; ++i) { 5: args.push(arguments[i]); 6: } 7: var m = this; 8: return function() { 9: for (var i=0, len = arguments.length; i < len; ++i) { 10: args.push(arguments[i]); 11: } 12: return m.apply(scope, args); 13: }; 14: } To partially curry this method we will call the curry method with the id parameter, then the request will callback on it with just the value.  Any additional parameters are appended to the method call. 1: for(var i=0;i<objects.length;i++) { 2: var id=objects[i].id; 3: Ajax.request('/some/data',{id: id}, updateGraph.curry(id)); 4: } As you can see, partial currying gives is a very useful tool and this simple method should be a part of every developer’s toolbox.

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• How to configure apache / php / postfix website emails when using vhosts?

  - by Alistair Buxton

  I have a LAMP webserver configured to serve multiple websites. Each virtual host has various PHP applications, mainly Wordpress. When users sign up to the Wordpress sites, email is sent by PHP through to postfix, and then on to the receiver. The problem is that postfix is identifying itself to the remote server with the contents of /etc/hostname, which is not a fully qualified domain name. Some mail servers reject this and the mail bounces. Additionally, the return path is being set to one of the vitual host domains, seemingly at random. I could set /etc/hostname to one of the website domain names, but then the emails from the other websites would have a wrong server in the headers, and this would not fix the return-path issue. Possibly related, apache2 says "could not determine the server's fully qualified domain name" on startup. How do I fix this so that each website can send email without revealing the other websites hosted on the server?

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